“Center pull” dispensers for dispensing flexible sheet material, such as paper towels and the like, are well known in the art. Center pull dispensers derive their name from the type of sheet material which they dispense. The sheet material is typically provided in the form of a center pull “web.” The material comprising the web is divided into discrete sheets by spaced-apart, transverse lines of perforations in the web. The web is typically rolled onto itself and then wound into a roll in which the lead end extends from the center of the roll. The web is unwound from the center of the roll by pulling on the lead end.
Center pull dispensers used to dispense this type of web material typically consist of a dispenser housing and a base within the housing for supporting a roll of the web material. A “nozzle” having a wall defining a generally conical inner passageway depends from the base or housing. The web is passed through the nozzle as it is pulled out of the dispenser by the user. The nozzle is sized such that the cross-sectional area of the narrowest portion of the passageway is slightly less than the effective cross-sectional area of the web material. The nozzle provides frictional resistance to movement of the web as it is pulled away from the dispenser by the user.
Web material is dispensed when the user grasps the leading end of the web outside the dispenser and pulls the leading end away from the dispenser. The pull force applied by the user causes the web to unwind from the center of the roll. If the dispenser operates as intended, resistance to the pull force applied by nozzle will cause a single sheet of the web material to tear along the perforation line outside of the dispenser between the nozzle and the leading edge of the web. Examples of center pull dispensers include U.S. Pat. No. 5,868,346 (Cobos), U.S. Pat. No. 5,765,718 (Grasso et al.), U.S. Pat. No. 5,762,287 (Schutz) and U.S. Pat. No. 5,205,455 (Moody).
Center pull dispensers of the prior art are subject to a number of important disadvantages. One disadvantage is that the fixed size of the nozzle passageway imposes certain limitations on the ability of the dispenser to accommodate the broad range of different grades and types of web material provided by different manufacturers. Commercially-available web material can vary greatly with respect to its thickness, size and physical characteristics all of which influence the effective cross-sectional area of the web.
For instance, if the nozzle is sized to accommodate thick, heavy weight paper having a relatively large effective cross-sectional area then the nozzle will not impart sufficient frictional force to light weight paper having a smaller effective cross-sectional area. Such improper sizing of the dispenser to the web material results in a condition known as “roping” in which plural sheets are dispensed from the dispenser on a single pull. Disadvantageously, roping results in waste of the web material and causes the web to be prematurely depleted increasing the cost to operate the dispenser.
Conversely, a nozzle sized to accommodate light weight paper would cause thicker, heavy weight paper to “bunch up” in the nozzle so that the paper is unable to flow smoothly through the nozzle. This form of improper sizing of the dispenser to the web material results in conditions known as “tabbing” or “short pulling.” Tabbing refers to a condition in which a small portion of the web sheet tears off in the user's hand and the user does not receive a sheet while short pulling involves a tearing of the web before the perforation thereby providing the user with more material than a tabbed sheet but less material than a full sheet. The tabbing and short pull conditions may make further removal of web from the dispenser difficult or impossible because the leading end of the web may be torn or too short to be grasped by a subsequent user.
A further disadvantage of the prior art dispensers is that movement of the web through the nozzle can cause excessive wear on the nozzle, particularly if the nozzle has an area sized too small for the effective cross-sectional area of the web. Excessive wear of the nozzle can reduce the nozzle's frictional resistance to the pull of the web resulting in the undesirable roping condition described above.
Efforts have been made to provide a dispenser capable of dispensing more than one type of sheet material each having different thicknesses, sizes and physical characteristics. However, these dispensers are not completely satisfactory for a number of important reasons. One disadvantage inherent in these types of dispensers is that the dispensers cannot be sized to the full range of commercially-available web material while another disadvantage involves the fact that these dispensers require undue manual adjustment. For example, the dispensers of U.S. Pat. No. 5,370,338 (Lewis) and U.S. Pat. No. 5,211,308 (Decker et al.) are provided with a limited number of differently-sized apertures which can be moved into registry with the nozzle thereby permitting limited adjustment of the nozzle area to the type of web material to be dispensed.
The dispenser of U.S. Pat. No. 5,749,492 (Petterson) is provided with manually-adjusted sizing rods or wall structure permitting the attendant to manually adjust the size of the aperture through which the web material is withdrawn from the dispenser. Further manual adjustment is required to re-set the rods or wall structure before a different type of web material can be dispensed.
The dispensers of U.S. Pat. No. 5,715,971 (Morand) and U.S. Pat. No. 5,246,137 (Schutz et al.) include a manually-positionable nozzle insert ring provided to permit the attendant to size the nozzle to the effective cross-sectional area of the paper. Disadvantageously, manual sizing of the rings is required. Moreover, the dispenser may become useless if the rings are lost or are inadvertently discarded.
Any requirement that the dispenser be manually adjusted to the effective cross-sectional area of the web material creates the likelihood that the dispenser nozzle or dispensing aperture will be set to a size unsuitable for the particular web material to be dispensed. This may result in roping or tabbing of the web material or in excessive wear to the dispenser. Further, any apparatus limiting the sizes of the aperture to one of several predetermined sizes restricts the range of web material potentially dispensable from the dispenser.
It would be a significant improvement in the art to provide a center pull dispenser apparatus with an improved dispenser mechanism that would reliably dispense different types of flexible sheet material thereby accommodating a range of different web material thicknesses, sizes and physical characteristics, which would self-adjust to the type of web material being dispensed and which would automatically compensate for wear thereby extending the operational life of the dispenser all resulting in improved dispenser performance and reduced costs to the operator.